165 lines
4.8 KiB
Plaintext
165 lines
4.8 KiB
Plaintext
* MOTOROLA MICROPROCESSOR & MEMORY TECHNOLOGY GROUP
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* M68000 Hi-Performance Microprocessor Division
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* M68040 Software Package
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*
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* M68040 Software Package Copyright (c) 1993, 1994 Motorola Inc.
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* All rights reserved.
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*
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* THE SOFTWARE is provided on an "AS IS" basis and without warranty.
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* To the maximum extent permitted by applicable law,
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* MOTOROLA DISCLAIMS ALL WARRANTIES WHETHER EXPRESS OR IMPLIED,
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* INCLUDING IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
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* PARTICULAR PURPOSE and any warranty against infringement with
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* regard to the SOFTWARE (INCLUDING ANY MODIFIED VERSIONS THEREOF)
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* and any accompanying written materials.
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*
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* To the maximum extent permitted by applicable law,
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* IN NO EVENT SHALL MOTOROLA BE LIABLE FOR ANY DAMAGES WHATSOEVER
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* (INCLUDING WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS
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* PROFITS, BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, OR
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* OTHER PECUNIARY LOSS) ARISING OF THE USE OR INABILITY TO USE THE
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* SOFTWARE. Motorola assumes no responsibility for the maintenance
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* and support of the SOFTWARE.
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*
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* You are hereby granted a copyright license to use, modify, and
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* distribute the SOFTWARE so long as this entire notice is retained
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* without alteration in any modified and/or redistributed versions,
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* and that such modified versions are clearly identified as such.
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* No licenses are granted by implication, estoppel or otherwise
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* under any patents or trademarks of Motorola, Inc.
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*
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* sgetem.sa 3.1 12/10/90
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*
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* The entry point sGETEXP returns the exponent portion
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* of the input argument. The exponent bias is removed
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* and the exponent value is returned as an extended
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* precision number in fp0. sGETEXPD handles denormalized
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* numbers.
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*
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* The entry point sGETMAN extracts the mantissa of the
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* input argument. The mantissa is converted to an
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* extended precision number and returned in fp0. The
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* range of the result is [1.0 - 2.0).
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*
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*
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* Input: Double-extended number X in the ETEMP space in
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* the floating-point save stack.
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*
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* Output: The functions return exp(X) or man(X) in fp0.
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*
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* Modified: fp0.
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*
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SGETEM IDNT 2,1 Motorola 040 Floating Point Software Package
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section 8
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include fpsp.h
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xref nrm_set
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*
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* This entry point is used by the unimplemented instruction exception
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* handler. It points a0 to the input operand.
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*
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*
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*
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* SGETEXP
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*
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xdef sgetexp
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sgetexp:
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move.w LOCAL_EX(a0),d0 ;get the exponent
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bclr.l #15,d0 ;clear the sign bit
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sub.w #$3fff,d0 ;subtract off the bias
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fmove.w d0,fp0 ;move the exp to fp0
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rts
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xdef sgetexpd
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sgetexpd:
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bclr.b #sign_bit,LOCAL_EX(a0)
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bsr nrm_set ;normalize (exp will go negative)
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move.w LOCAL_EX(a0),d0 ;load resulting exponent into d0
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sub.w #$3fff,d0 ;subtract off the bias
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fmove.w d0,fp0 ;move the exp to fp0
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rts
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*
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*
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* This entry point is used by the unimplemented instruction exception
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* handler. It points a0 to the input operand.
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*
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*
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*
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* SGETMAN
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*
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*
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* For normalized numbers, leave the mantissa alone, simply load
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* with an exponent of +/- $3fff.
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*
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xdef sgetman
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sgetman:
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move.l USER_FPCR(a6),d0
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andi.l #$ffffff00,d0 ;clear rounding precision and mode
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fmove.l d0,fpcr ;this fpcr setting is used by the 882
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move.w LOCAL_EX(a0),d0 ;get the exp (really just want sign bit)
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or.w #$7fff,d0 ;clear old exp
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bclr.l #14,d0 ;make it the new exp +-3fff
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move.w d0,LOCAL_EX(a0) ;move the sign & exp back to fsave stack
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fmove.x (a0),fp0 ;put new value back in fp0
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rts
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*
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* For denormalized numbers, shift the mantissa until the j-bit = 1,
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* then load the exponent with +/1 $3fff.
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*
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xdef sgetmand
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sgetmand:
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move.l LOCAL_HI(a0),d0 ;load ms mant in d0
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move.l LOCAL_LO(a0),d1 ;load ls mant in d1
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bsr shft ;shift mantissa bits till msbit is set
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move.l d0,LOCAL_HI(a0) ;put ms mant back on stack
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move.l d1,LOCAL_LO(a0) ;put ls mant back on stack
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bra.b sgetman
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*
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* SHFT
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*
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* Shifts the mantissa bits until msbit is set.
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* input:
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* ms mantissa part in d0
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* ls mantissa part in d1
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* output:
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* shifted bits in d0 and d1
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shft:
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tst.l d0 ;if any bits set in ms mant
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bne.b upper ;then branch
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* ;else no bits set in ms mant
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tst.l d1 ;test if any bits set in ls mant
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bne.b cont ;if set then continue
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bra.b shft_end ;else return
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cont:
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move.l d3,-(a7) ;save d3
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exg d0,d1 ;shift ls mant to ms mant
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bfffo d0{0:32},d3 ;find first 1 in ls mant to d0
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lsl.l d3,d0 ;shift first 1 to integer bit in ms mant
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move.l (a7)+,d3 ;restore d3
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bra.b shft_end
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upper:
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movem.l d3/d5/d6,-(a7) ;save registers
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bfffo d0{0:32},d3 ;find first 1 in ls mant to d0
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lsl.l d3,d0 ;shift ms mant until j-bit is set
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move.l d1,d6 ;save ls mant in d6
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lsl.l d3,d1 ;shift ls mant by count
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move.l #32,d5
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sub.l d3,d5 ;sub 32 from shift for ls mant
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lsr.l d5,d6 ;shift off all bits but those that will
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* ;be shifted into ms mant
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or.l d6,d0 ;shift the ls mant bits into the ms mant
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movem.l (a7)+,d3/d5/d6 ;restore registers
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shft_end:
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rts
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end
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